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Aseprite MCP

Aseprite MCP

by MalloyTheDev
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

set_cel_opacity

Adjust a cel's opacity in an Aseprite animation by specifying a 0-255 value for the target layer and frame.

Instructions

Set a cel's opacity (0-255).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "filename": "<filename>",
      "layer": "<layer>",
      "frame": "<frame>",
      "opacity": "<opacity>"
    },
    "name": "set_cel_opacity"
  }
}

Input Schema

NameRequiredDescriptionDefault
frameYes
layerYes
opacityYes
filenameYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed5 schema fields changedv0.10.0
    • removedInput schema / properties / filename / title
      Removed value: -"Filename"
    • removedInput schema / properties / frame / title
      Removed value: -"Frame"
    • removedInput schema / properties / layer / title
      Removed value: -"Layer"
    • removedInput schema / properties / opacity / title
      Removed value: -"Opacity"
    • removedInput schema / title
      Removed value: -"set_cel_opacityArguments"
  2. First observedv0.7.0

TDQS

C2.9/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare it's a non-read-only, closed-world mutation. The description adds the 0-255 range constraint, which is useful behavioral context beyond annotations, but doesn't explain effects on linked cels, clamping, or persistence.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

One front-loaded sentence with no wasted words. For a simple setter, this is concise, though it could arguably afford a bit more detail on parameters without becoming verbose.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 4-parameter mutation with no schema descriptions and no output schema, the description is far too sparse. It identifies the operation and one parameter range but leaves the agent without necessary context on how to identify the target cel or interpret the other parameters.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0%, so the description must compensate. It only clarifies the 'opacity' parameter's range (0-255), leaving filename, layer, and frame completely undocumented—the agent has no semantic guidance for three of four required parameters.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Set') and resource ('cel's opacity'), clearly distinguishing it from sibling setters like set_cel_position or set_cel_z_index by naming the property. It stops short of 5 because it doesn't explicitly reference alternatives or scope (e.g., which cel).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool versus alternatives such as set_properties or set_cel_position, nor any prerequisites. The simple setter nature implies usage, but no explicit context is given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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